Gutenberg Open Science

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ZeitschriftenaufsatzAccess status: Open Access ,
Volume uptake of carbonyls during diffusional ice crystal growth
(2025) Seymore, Jackson; Szakáll, Miklós; Theis, Alexander; Mitra, Subir K.; Borchers, Christine; Hoffmann, Thorsten
Carbonyls are highly relevant atmospheric constituents that influence tropospheric photochemistry and oxidative capacity. They can be removed from the upper troposphere via ice phase deposition scavenging. The gas-volume uptake coefficients for 14 different carbonyl compounds were determined using a flowtube apparatus. Ice crystals were grown from vapor deposition in the presence of gas phase carbonyls at −20, −30, and −40 °C. Using van't Hoff analysis, the entropy and enthalpy of uptake were determined. An inverse relationship between uptake coefficients and temperature was observed for all species except methyl vinyl ketone. A linear correlation between ΔS and ΔH arose which was statistically validated and determined with 99 % confidence to not be a statistical artifact. This compensation behavior could be an indication of a surface liquid layer or quasi-liquid layer behavior involved in the uptake process and could also indicate a single dominant influence on a compound's uptake. The most significant physicochemical properties correlated with uptake were identified to be vapor pressure and molar mass, which indicate that smaller compounds with higher vapor pressures are more readily taken into the ice phase. The volume uptake coefficients observed here are below the 10 mol m−3 Pa−1 threshold given by Crutzen and Lawrence (2000) to be considered a substantial atmospheric removal process.
ZeitschriftenaufsatzAccess status: Open Access ,
The TropoPause Composition TOwed Sensor Shuttle (TPC-TOSS) : a new airborne dual platform approach for atmospheric composition measurements at the tropopause
(2025) Bozem, Heiko; Joppe, Philipp; Li, Yun; Emig, Nicolas; Afchine, Armin; Breuninger, Anna; Curtius, Joachim; Hofmann, Stefan; Ismayil, Sadath; Kandler, Konrad; Kunkel, Daniel; Kutschka, Arthur; Lachnitt, Hans-Christoph; Petzold, Andreas; Richter, Sarah; Röschenthaler, Timo; Rolf, Christian; Schneider, Lisa; Schneider, Johannes; Vogel, Alexander; Hoor, Peter
In this paper we introduce the new TropoPause Composition TOwed Sensor Shuttle (TPC-TOSS), which constitutes an advanced development of the AIRcraft TOwed Sensor Shuttle (AIRTOSS), introduced by Frey et al. (2009). As part of a tandem measurement platform with a Learjet 35A, both platforms were equipped with redundant instruments for co-located measurements of aerosol size distribution (Ultra-High Sensitivity Aerosol Spectrometer, UHSAS), ozone (2BTech model 205), cloud particles (Back-Scatter Cloud Probe, BCP), as well as relative humidity, temperature and pressure. To measure the exact position of the two platforms as well as the relative distance of the TPC-TOSS to the Learjet a Global Positioning System (GPS) is installed on both platforms. Two identical Inertial Navigation Systems (INS) further allow to monitor attitude angles (roll, pitch, and heading) and accelerations. Laboratory tests before and ground tests as well as in-flight tests during the intensive operation period show a good agreement of the ozone and temperature measurements of better than 4.2 ppbv +1.1 % (ozone) and 0.5 °C (temperature) at a noise level of ± (2 ppbv + 0.5 %) for 2 s data (ozone) and ± 0.1 K for 1 Hz data (temperature). Stability of the ozone monitor mounted in the TPC-TOSS has been tested and is estimated to be 2.2 ppbv (offset, 1σ) and 0.7 % (gain, 1σ), respectively, based on the drift of offset and gain during regular calibrations between measurement flights in the two weeks operation period. The new TPC-TOSS was successfully flown during the TPEx I (TropoPause composition gradients and mixing Experiment) mission in June 2024 and performed four flights covering the altitude range between 6.4 and 10.9 km. The tropopause was crossed several times as evident from different temperature and ozone gradients as well as gradients of the aerosol number concentration. With the setup we are able to resolve transient stability and composition gradients ranging from almost zero or even negative to strong positive gradients of up to 25 K km−1 for potential temperature and from inverted to strong positive vertical gradients of ozone of up to 800 ppbv km−1, respectively. These gradients are caused by transport and mixing due to convection or shear induced turbulence at the tropopause.
ZeitschriftenaufsatzAccess status: Open Access ,
The frosty frontier : redefining the mid-latitude tropopause using the relative humidity over ice
(2025) Reutter, Philipp; Spichtinger, Peter
The tropopause represents a central feature of the atmospheric vertical structure, marking the transition between the troposphere and stratosphere. While common definitions rely on quantities conserved under adiabatic changes, diabatic effects, resulting from radiation, cloud processes or turbulence are also decisive for the tropopause structure. Therefore, we propose a new definition based on the vertical gradient of the relative humidity with respect to ice (RHi). RHi is the key variable for ice cloud formation and incorporates both diabatic and adiabatic processes. Based on high-resolution radiosonde data, we can show that our RHi-GT-based definition is generally consistent with, and often provides a clearer characterization than the thermal tropopause. This is not only evident in individual vertical profiles, but also when looking at statistics of many profiles with a tropopause-relative height axis. Last but not least, the robust and simple calculation of our definition makes it an ideal tool for studies involving the tropopause.